Bitmap Join Index not working when defined for "multiple columns"

Oracle 11g documentation says "you can create a bitmap join index on more than one column from a single dimension table."   However our bitmap join indexes are only working when we define them for a single column.  Has anyone else experienced this?

The following example works fine.  A query with customers.cust_gender in the Where clause will hit the index.  Works great!

CREATE BITMAP INDEX sales_cust_gender_ms_bjix
ON sales(customers.cust_gender)
FROM sales, customers
WHERE sales.cust_id = customers.cust_id
LOCAL NOLOGGING COMPUTE STATISTICS;

However the the following example does not work.  A query with customers.cust_gender or customers.cust_marital_status in the Where clause does NOT hit the index.  Not sure why.